Found on Australia’s Great Barrier Reef, the new species of hermaphroditic sea slug­­ — bright yellow, red and white and just a few millimeters long — has the double set of penile organs typical of Siphopteron slugs. Yet the new slugs deploy them in a novel way, says marine behavioral ecologist Rolanda Lange of Monash University in Clayton, Australia.

When the as-yet-unnamed slugs mate, one organ delivers the sperm to the female opening on another slug’s body. Seconds after partners position their structures for simultaneous sperm transfer, the slugs each insert a second organ, a needlelike stylet. Each slug plunges it like a syringe into the area around the other’s eyes, Lange and her colleagues report November 12 in the Proceedings of the Royal Society B.

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